It is the object of this invention to provide a method and an apparatus for forming the required arcuate radially-extended locking projections on the pipe ends at the actual point of assembly of the pipes into a pipeline assembly, thus permitting the ready fabrication of pipeline assemblies from standard stock lengths of pipe, or from non-standard lengths of pipe cut from standard stock lengths of pipe.
By forming the arcuate locking projections on to the pipes at the point of assembly rather than at the point of manufacture, the intransit handling of the pipes is greatly facilitated, and, the problem of intransit damage of the arcuate locking projections is eliminated in its entirety.
While the formation of the arcuate projections on the pipes at the point of assembly of the pipes would appear, superficially, to be a relatively simple matter, the finished form and relative position of the arcuate projections is in fact a matter requiring substantial accuracy, for example, if the projections are too close to the pipe ends then the coupling will not be in the correct relative position so that the gasket may overhang the pipe ends and leakage will occur, alternately, if the projections are skewed to the longitudinal axis of the pipe, difficulty will be encountered in assembling the coupling with possible malfunction and leakage occuring. Also, for proper performance of the coupling it is desirable that the projections lie in the same plane, perpendicular to the longitudinal axis of the pipes. Further, many of the pipes include a longitudinal seam. In such instances, the arcuate projections must be set off from the seam line. Additionally, distortion of the pipe from its truly circular condition must be minimized, and axial or radial displacement or distortion of the pipe ends should be avoided, or incomplete seating of the gasket can occur and the compressive stressing of the gasket throughout its circumference will not be constant, such conditions militating against satisfactory sealing of the pipe ends at the coupling.